The code is working on my 3.24.100 Frege Repl, and I am trying to reinvent ContT monad transformer in Frege now, hope I can learn more about Haskell
在 2017年11月23日星期四 UTC+8上午10:07:07，zhou...@163.com写道： > > No big deal, only recording my progress striving to understand monad and > monad transformer with this tutorial > https://en.wikibooks.org/wiki/Haskell/Continuation_passing_style and this > https://wiki.haskell.org/All_about_monads#The_Continuation_monad > > > data Cont r a = Cont { runCont :: ((a -> r) -> r)} > > instance Monad (Cont r) where > pure x = cont ($ x) > s >>= f = cont $ \c -> runCont s $ \x -> runCont (f x) c > > cont :: ((a -> r) -> r) -> Cont r a > cont f = Cont { runCont = f} > > runCont :: Cont r a -> (a -> r) -> r > runCont c = Cont.runCont c > > callCC f = cont $ \h -> runCont (f (\a -> cont $ \_ -> h a)) h > > fun :: Int -> String > fun n = (`runCont` id) $ do > str <- callCC $ \exit1 -> do > when (n < 10) (exit1 (show n)) > let ns = map digitToInt (unpacked (show (n `div` 2))) > n' <- callCC $ \exit2 -> do > when ((length ns) < 3) (exit2 (length ns)) > when ((length ns) < 5) (exit2 n) > when ((length ns) < 7) $ do > let ns` = map intToDigit (reverse ns) > exit1 $ packed $ (dropWhile (== '0') ns') > return $ sum ns > return $ "(ns = " ++ (show ns) ++ ") " ++ (show n') > return $ "Answer: " ++ str > > > -- You received this message because you are subscribed to the Google Groups "Frege Programming Language" group. To unsubscribe from this group and stop receiving emails from it, send an email to frege-programming-language+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
